Making calculations on off stochiometric composition, the main challenge arise is to make the supercell, and deal the large number of atoms in unit cell. The next challenge is to make the SCF calculations, which itself is time consuming in case you have more number of atoms. To overcome such problems in terms of easy and fast calculations green function based codes are very much efficient. The name of dft codes are Akai-kkr developed by japanese group, and spr kkr developed by German group (please check). The most important point which one can always look in disorder system is the local disorder. You can use these codes to calculate the electronic structure. With local magnetic disorder calculations you can also get the Curie temperature by using the Mean Field Theory based formula. I guess it will help you. In case you wish to learn the code or need any further help, I can try my best to help you within my understanding and level of expertise.

Thank you very much, Saurabh Singh. Your inputs are invaluable to me. I am trying to obtain elastic constants using DFT calculation. Yes, definitely ....I want to learn and implement those codes on my system. Can we calculate elastic constants of materials using those codes?

Regards

Subha Sanket Panda